The availability of a sealed neutron source, Californium-252, with the high relative biological effectiveness (RBE) of fission neutrons indicated its potential value as a supplement to radium-226 for treatment of cancer located in a body cavity. The site where these sources would be most likely used is in the uterine-cervix but the tissues adjacent to that organ, the rectum and urinary bladder, are at risk from the gamma radiation in a radium treatment and are probably more sensitive to the effects of neutrons. Consequently, the response of these and other normal tissues that may be irradiated during treatment should be determined, especially at intervals from 2-5 years after exposure when complications are most frequently observed. The experimental animal we have used to study the acute effects of intracervical irradiation with Cf252 in order to establish an RBE for Californium neutrons was the miniature swine. The spatial relationship between the cervix and the tissues at risk in a therapeutic treatment for cervical cancer in humans is apparently similar to that of the miniature pig. The responses of these normal tissues was followed by proctoscopy, intravenous pyelography (IVP) and cystocopy. The frequency of rectal ulcers and ureteral structures at intervals during the first year after treatment with Cf252 made it necessary to reduce the fractionated dose from 2800 rad measured at 2.0 cm lateral to the source center to 1600 rad. Comparable reductions of dose from 10,000 rad to 5000 rad were made for Ra226 treatments but the frequency of complications during the acute phase of injury was not as limiting as it was for Cf252. The incidence of these effects at a few years post- exposure is a most important criterian for judging the safety of encapsulated Cf252 because of the suspected poor repair potential of neutron irradiated tissues.